[kallelsgp1200]

just tore down then engine on my 98 gp1200 and cly #3 was destroyed and i have lots of this on this and onther forems before i build this engine i was wondering what causes this so i can avoid this again...



It was full of oil and didn't get hot but it only happed in #3?

 

[GCwaverunner]

Could be one of many things. Apart from all the must do's when you rebuild the engine like checking oil injection system and cleaning the carbs, generally on those non power valve 1200's the ring will get caught in the exhaust port when the engine is getting a bit old. Once you get it re-sleeved you can die grind a small shamfer in the top of the exhaust port. Don't change the dynamics of it much if you want to keep it OEM but it works.

 

[bigair64]

Things to check/replace in order of difficulty:
1) Crease on plastic carburator pump valve (about $1) - leaky valve = lean mix at high speed = piston seize
2) Intake reed valves ($25) - leaky reeds = lean mix......
3) Twisted crank ($$$) - twisted crank = premature detonation in #3 = high heat = piston seize

 

[onefastmx5]

If the big end rod bearing is seized on I'd defintely take a peak at the injection hose for an obstruction.